Signal transmission/reception method between terminal and base station in wireless communication system supporting narrowband internet of things, and device supporting same

ABSTRACT

Disclosed are a signal transmission/reception method between a terminal and a base station in a wireless communication system supporting narrowband Internet of Things (NB-IoT), and a device supporting same. More specifically, disclosed is a description of a signal transmission/reception method between a terminal and a base station when a wireless communication system supporting NB-IoT is a time division duplex (TDD) system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/543,119, filed on Aug. 16, 2019, which is a continuation ofInternational Application No. PCT/KR2018/002015, filed on Feb. 19, 2018,which claims the benefit of U.S. Provisional Application No. 62/547,768,filed on Aug. 19, 2017, and U.S. Provisional Application No. 62/460,103,filed on Feb. 17, 2017. The disclosures of the prior applications areincorporated by reference in their entirety.

TECHNICAL FIELD

The following description relates to a wireless communication system,and more particularly, to a signal transmission/reception method betweena terminal and a base station in a wireless communication systemsupporting Narrowband Internet of Things (NB-IoT), and devicessupporting the same.

More specifically, in the following description includes description ofa method of transmitting and receiving signals between a terminal and abase station when a wireless communication system supporting theNarrowband Internet of Things (NB-IoT) is a time division duplex (TDD)system.

BACKGROUND

Wireless access systems have been widely deployed to provide varioustypes of communication services such as voice or data. In general, awireless access system is a multiple access system that supportscommunication of multiple users by sharing available system resources (abandwidth, transmission power, etc.) among them. For example, multipleaccess systems include a Code Division Multiple Access (CDMA) system, aFrequency Division Multiple Access (FDMA) system, a Time DivisionMultiple Access (TDMA) system, an Orthogonal Frequency Division MultipleAccess (OFDMA) system, and a Single Carrier Frequency Division MultipleAccess (SC-FDMA) system.

In particular, Internet of Things (IoT) communication technology isnewly proposed. Here, IoT refers to communication that does not involvehuman interaction. A way to introduce such IoT communication technologyin a cellular-based LTE system is further under discussion.

The conventional Long Term Evolution (LTE) system has been designed tosupport high-speed data communication and thus has been regarded as anexpensive communication technology for people.

However, IoT communication technology can be widely used only if thecost is reduced.

There have been discussions about reducing the bandwidth as a way toreduce cost. However, to reduce the bandwidth, a new frame structureshould be designed in the time domain, and the issue of interferencewith the existing neighboring LTE terminals should also be considered.

SUMMARY

An object of the present invention is to provide a method fortransmitting/receiving a synchronization signal between a terminal and abase station in a wireless communication system supporting narrowbandInternet of Things.

In particular, an object of the present invention is to provide a methodfor transmitting/receiving a synchronization signal between a terminaland a base station when the wireless communication system is a TDDsystem.

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present disclosure are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present disclosure could achieve will be more clearlyunderstood from the following detailed description.

The present invention provides a method and devices fortransmitting/receiving signals between a terminal and a base station ina wireless communication system supporting narrowband Internet orThings.

In one aspect of the present invention, provided herein is a method ofreceiving, by a terminal, a signal from a base station in a wirelesscommunication system supporting Narrow Band-Internet of Things (NB-IoT),the method including receiving a Narrowband Primary SynchronizationSignal (NPSS) and a Narrowband Secondary Synchronization Signal (NSSS)through a first carrier during different sub-time intervals, wherein onetime interval includes a plurality of sub-time intervals, wherein theNPSS is received during an X-th (where X is a natural number) sub-timeinterval in every time interval, and the NSSS is received during a Y-th(where Y is a natural number) sub-time interval in a corresponding timeinterval with a periodicity of two time intervals; and receiving SystemInformation Block 1-Narrow Band (SIB1-NB) through a second carrierdifferent from the first carrier during a Y-th sub-time interval in acorresponding time interval with a periodicity of one or more timeintervals.

In another aspect of the present invention, provided herein is a methodof transmitting, by a base station, a signal to a terminal in a wirelesscommunication system supporting Narrow Band-Internet of Things (NB-IoT),the method including transmitting a Narrowband Primary SynchronizationSignal (NPSS) and a Narrowband Secondary Synchronization Signal (NSSS)through a first carrier during different sub-time intervals, wherein onetime interval includes a plurality of sub-time intervals, wherein theNPSS is transmitted during an X-th (where X is a natural number)sub-time interval in every time interval, and the NSSS is transmittedduring a Y-th (where Y is a natural number) sub-time interval in acorresponding time interval with a periodicity of two time intervals;and transmitting System Information Block 1-Narrow Band (SIB1-NB)through a second carrier different from the first carrier during a Y-thsub-time interval in a corresponding time interval with a periodicity ofone or more time intervals.

In another aspect of the present invention, provided herein is aterminal for receiving a signal from a base station in a wirelesscommunication system supporting Narrow Band-Internet of Things (NB-IoT),the terminal including a receiver; and a processor operatively coupledto the receiver, wherein the processor is configured to receive aNarrowband Primary Synchronization Signal (NPSS) and a NarrowbandSecondary Synchronization Signal (NSSS) through a first carrier duringdifferent sub-time intervals, wherein one time interval includes aplurality of sub-time intervals, wherein the NPSS is received during anX-th (where X is a natural number) sub-time interval in every timeinterval, and the NSSS is received during a Y-th (where Y is a naturalnumber) sub-time interval in a corresponding time interval with aperiodicity of two time intervals; and receive System Information Block1-Narrow Band (SIB1-NB) through a second carrier different from thefirst carrier during a Y-th sub-time interval in a corresponding timeinterval with a periodicity of one or more time intervals.

In another aspect of the present invention, provided herein is a basestation for transmitting a signal to a terminal in a wirelesscommunication system supporting Narrow Band-Internet of Things (NB-IoT),the base station including a transmitter; and a processor operativelycoupled to the transmitter.

The processor is configured to transmit a Narrowband PrimarySynchronization Signal (NPSS) and a Narrowband Secondary SynchronizationSignal (NSSS) through a first carrier during different sub-timeintervals, wherein one time interval includes a plurality of sub-timeintervals, wherein the NPSS is transmitted during an X-th (where X is anatural number) sub-time interval in every time interval, and the NSSSis transmitted during a Y-th (where Y is a natural number) sub-timeinterval in a corresponding time interval with a periodicity of two timeintervals; and transmit System Information Block 1-Narrow Band (SIB1-NB)through a second carrier different from the first carrier during a Y-thsub-time interval in a corresponding time interval with a periodicity ofone or more time intervals.

Herein, the first carrier may correspond to an anchor-carrier, and thesecond carrier may correspond to a non-anchor carrier.

In addition, X and Y may be set to different values.

The one time interval may be one radio frame, and each of the sub-timeintervals may be one subframe, wherein the radio frame may include 10subframes.

In this case, X may be 6, and Y may be 1.

The periodicity of one or more time intervals for transmitting theSIB1-NB may correspond to a periodicity of two time intervals or aperiodicity of four time intervals.

The SIB1-NB may be received through the second carrier during the Y-thsub-time interval in a time interval in which the NSSS is nottransmitted.

The wireless communication system may be a time division duplex (TDD)system.

In this case, when the wireless communication system is a TDD systemdefined in a 3GPP Long Term Evolution (LTE) system, the wirelesscommunication system may not support uplink/downlink configuration 0 forone radio frame defined in the 3GPP LTE system.

It is to be understood that both the foregoing general description andthe following detailed description of the present disclosure areexemplary and explanatory and are intended to provide furtherexplanation of the disclosure as claimed.

As is apparent from the above description, the embodiments of thepresent invention have the following effects.

According to embodiments of the present invention, a terminal and a basestation may transmit and receive NPSS and NSSS through an anchorcarrier, while transmitting and receiving signals through a non-anchorcarrier in SIB1-NB.

In particular, in the case of the LTE TDD system, it is difficult forthe terminal to know an uplink/downlink configuration established by thebase station before receiving SIB information, and accordingly theterminal and the base station should are restricted to transmit andreceive the NPSS, the NSSS, the SIB1-NB, and the like through a downlinksubframe that is applicable in common to all uplink/downlinkconfigurations. In contrast, the present invention provides a method forperforming signal transmission/reception by minimizing collision betweensignals within limited downlink resources, and thus the terminal and thebase station may transmit/receive the signals using an optimizedtransmission/reception method.

It will be appreciated by persons skilled in the art that the effectsthat can be achieved with the present disclosure are not limited to whathas been particularly described hereinabove and other advantages of thepresent disclosure will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings. In other words, unintended effects according to implementationof the present invention may also be obtained by those skilled in theart from the embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, provide embodiments of the presentinvention together with detail explanation. Yet, a technicalcharacteristic of the present invention is not limited to a specificdrawing. Characteristics disclosed in each of the drawings are combinedwith each other to configure a new embodiment. Reference numerals ineach drawing correspond to structural elements.

FIG. 1 is a diagram illustrating physical channels and a signaltransmission method using the physical channels.

FIGS. 2A and 2B are diagrams illustrating exemplary radio framestructures.

FIG. 3 is a diagram illustrating an exemplary resource grid for theduration of a downlink slot.

FIG. 4 is a diagram illustrating an exemplary structure of an uplinksubframe.

FIG. 5 is a diagram illustrating an exemplary structure of a downlinksubframe.

FIG. 6 is a diagram illustrating a self-contained subframe structureapplicable to the present invention.

FIGS. 7 and 8 are diagrams illustrating representative methods forconnecting TXRUs to antenna elements.

FIG. 9 is a diagram schematically illustrating an exemplary hybridbeamforming structure from the perspective of transceiver units (TXRUs)and physical antennas according to the present invention.

FIG. 10 is a diagram schematically illustrating an exemplary beamsweeping operation for a synchronization signal and system informationin a downlink (DL) transmission procedure according to the presentinvention.

FIG. 11 is a diagram schematically illustrating arrangement of anin-band anchor carrier for an LTE bandwidth of 10 MHz.

FIG. 12 is a diagram schematically illustrating positions where aphysical downlink channel and a downlink signal are transmitted in anFDD LTE system.

FIG. 13 is a diagram illustrating exemplary resource allocation of anNB-IoT signal and an LTE signal in an in-band mode.

FIGS. 14 to 17 are diagrams illustrating various examples of specialsub-frame configuration.

FIG. 18 is a diagram illustrating subframe configuration and the meaningof notations according to the CP length in FIGS. 14 to 17.

FIG. 19 is a diagram schematically illustrating a signaltransmission/reception method between a terminal and a base stationaccording to the present invention.

FIG. 20 is a diagram showing configuration of a terminal and a basestation in which the proposed embodiments are implementable.

DETAILED DESCRIPTION

The embodiments of the present disclosure described below arecombinations of elements and features of the present disclosure inspecific forms. The elements or features may be considered selectiveunless otherwise mentioned. Each element or feature may be practicedwithout being combined with other elements or features. Further, anembodiment of the present disclosure may be constructed by combiningparts of the elements and/or features. Operation orders described inembodiments of the present disclosure may be rearranged. Someconstructions or elements of any one embodiment may be included inanother embodiment and may be replaced with corresponding constructionsor features of another embodiment.

In the description of the attached drawings, a detailed description ofknown procedures or steps of the present disclosure will be avoided lestit should obscure the subject matter of the present disclosure. Inaddition, procedures or steps that could be understood to those skilledin the art will not be described either.

Throughout the specification, when a certain portion “includes” or“comprises” a certain component, this indicates that other componentsare not excluded and may be further included unless otherwise noted. Theterms “unit”, “-or/er” and “module” described in the specificationindicate a unit for processing at least one function or operation, whichmay be implemented by hardware, software or a combination thereof. Inaddition, the terms “a or an”, “one”, “the” etc. may include a singularrepresentation and a plural representation in the context of the presentdisclosure (more particularly, in the context of the following claims)unless indicated otherwise in the specification or unless contextclearly indicates otherwise.

In the embodiments of the present disclosure, a description is mainlymade of a data transmission and reception relationship between a BaseStation (BS) and a User Equipment (UE). A BS refers to a terminal nodeof a network, which directly communicates with a UE. A specificoperation described as being performed by the BS may be performed by anupper node of the BS.

Namely, it is apparent that, in a network comprised of a plurality ofnetwork nodes including a BS, various operations performed forcommunication with a UE may be performed by the BS, or network nodesother than the BS. The term ‘BS’ may be replaced with a fixed station, aNode B, an evolved Node B (eNode B or eNB), gNode B (gNB), an AdvancedBase Station (ABS), an access point, etc.

In the embodiments of the present disclosure, the term terminal may bereplaced with a UE, a Mobile Station (MS), a Subscriber Station (SS), aMobile Subscriber Station (MSS), a mobile terminal, an Advanced MobileStation (AMS), etc.

A transmission end is a fixed and/or mobile node that provides a dataservice or a voice service and a reception end is a fixed and/or mobilenode that receives a data service or a voice service. Therefore, a UEmay serve as a transmission end and a BS may serve as a reception end,on an UpLink (UL). Likewise, the UE may serve as a reception end and theBS may serve as a transmission end, on a DownLink (DL).

The embodiments of the present disclosure may be supported by standardspecifications disclosed for at least one of wireless access systemsincluding an Institute of Electrical and Electronics Engineers (IEEE)802.xx system, a 3rd Generation Partnership Project (3GPP) system, a3GPP Long Term Evolution (LTE) system, 3GPP 5G NR system and a 3GPP2system. In particular, the embodiments of the present disclosure may besupported by the standard specifications, 3GPP TS 36.211, 3GPP TS36.212, 3GPP TS 36.213, 3GPP TS 36.321, 3GPP TS 36.331, 3GPP TS 38.211,3GPP TS 38.212, 3GPP TS 38.213, 3GPP TS 38.321 and 3GPP TS 38.331. Thatis, the steps or parts, which are not described to clearly reveal thetechnical idea of the present disclosure, in the embodiments of thepresent disclosure may be explained by the above standardspecifications. All terms used in the embodiments of the presentdisclosure may be explained by the standard specifications.

Reference will now be made in detail to the embodiments of the presentdisclosure with reference to the accompanying drawings. The detaileddescription, which will be given below with reference to theaccompanying drawings, is intended to explain exemplary embodiments ofthe present disclosure, rather than to show the only embodiments thatcan be implemented according to the disclosure.

The following detailed description includes specific terms in order toprovide a thorough understanding of the present disclosure. However, itwill be apparent to those skilled in the art that the specific terms maybe replaced with other terms without departing the technical spirit andscope of the present disclosure.

For example, the term, TxOP may be used interchangeably withtransmission period or Reserved Resource Period (RRP) in the same sense.Further, a Listen-Before-Talk (LBT) procedure may be performed for thesame purpose as a carrier sensing procedure for determining whether achannel state is idle or busy, CCA (Clear Channel Assessment), CAP(Channel Access Procedure).

Hereinafter, 3GPP LTE/LTE-A systems are explained, which are examples ofwireless access systems.

The embodiments of the present disclosure can be applied to variouswireless access systems such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), SingleCarrier Frequency Division Multiple Access (SC-FDMA), etc.

CDMA may be implemented as a radio technology such as UniversalTerrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented asa radio technology such as Global System for Mobile communications(GSM)/General packet Radio Service (GPRS)/Enhanced Data Rates for GSMEvolution (EDGE). OFDMA may be implemented as a radio technology such asIEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Evolved UTRA(E-UTRA), etc.

UTRA is a part of Universal Mobile Telecommunications System (UMTS).3GPP LTE is a part of Evolved UMTS (E-UMTS) using E-UTRA, adopting OFDMAfor DL and SC-FDMA for UL. LTE-Advanced (LTE-A) is an evolution of 3GPPLTE. While the embodiments of the present disclosure are described inthe context of a 3GPP LTE/LTE-A system in order to clarify the technicalfeatures of the present disclosure, the present disclosure is alsoapplicable to an IEEE 802.16e/m system, etc.

1. 3GPP LTE/LTE-A System 1.1. Physical Channels and Signal Transmissionand Reception Method Using the Same

In a wireless access system, a UE receives information from a basestation on a DL and transmits information to the base station on a UL.The information transmitted and received between the UE and the basestation includes general data information and various types of controlinformation. There are many physical channels according to thetypes/usages of information transmitted and received between the basestation and the UE.

FIG. 1 illustrates physical channels and a general signal transmissionmethod using the physical channels, which may be used in embodiments ofthe present disclosure.

When a UE is powered on or enters a new cell, the UE performs initialcell search (S11). The initial cell search involves acquisition ofsynchronization to the base station. Specifically, the UE synchronizesits timing to the base station and acquires information such as a cellIdentifier (ID) by receiving a Primary Synchronization Channel (P-SCH)and a Secondary Synchronization Channel (S-SCH) from the base station.

Then the UE may acquire information broadcast in the cell by receiving aPhysical Broadcast Channel (PBCH) from the base station.

During the initial cell search, the UE may monitor a DL channel state byreceiving a Downlink Reference Signal (DL RS).

After the initial cell search, the UE may obtain more detailed systeminformation by receiving a Physical Downlink Control Channel (PDCCH) andreceiving a Physical Downlink Shared Channel (PDSCH) based oninformation of the PDCCH (S12).

To complete connection to the base station, the UE may perform a randomaccess procedure with the base station (S13 to S16). In the randomaccess procedure, the UE may transmit a preamble on a Physical RandomAccess Channel (PRACH) (S13) and may receive a PDCCH and a PDSCHassociated with the PDCCH (S14). In the case of contention-based randomaccess, the UE may additionally perform a contention resolutionprocedure including transmission of an additional PRACH (S15) andreception of a PDCCH signal and a PDSCH signal corresponding to thePDCCH signal (S16).

After the above procedure, the UE may receive a PDCCH and/or a PDSCHfrom the base station (S17) and transmit a Physical Uplink SharedChannel (PUSCH) and/or a Physical Uplink Control Channel (PUCCH) to thebase station (S18), in a general UL/DL signal transmission procedure.

Control information that the UE transmits to the base station isgenerically called Uplink Control Information (UCI). The UCI includes aHybrid Automatic Repeat and reQuest Acknowledgement/NegativeAcknowledgement (HARQ-ACK/NACK), a Scheduling Request (SR), a ChannelQuality Indicator (CQI), a Precoding Matrix Index (PMI), a RankIndicator (RI), etc.

In the LTE system, UCI is generally transmitted on a PUCCH periodically.However, if control information and traffic data should be transmittedsimultaneously, the control information and traffic data may betransmitted on a PUSCH. In addition, the UCI may be transmittedaperiodically on the PUSCH, upon receipt of a request/command from anetwork.

1.2. Resource Structure

FIGS. 2A and 2B illustrate exemplary radio frame structures used inembodiments of the present disclosure.

FIG. 2A illustrates frame structure type 1. Frame structure type 1 isapplicable to both a full Frequency Division Duplex (FDD) system and ahalf FDD system.

One radio frame is 10 ms (Tf=307200·Ts) long, including equal-sized 20slots indexed from 0 to 19. Each slot is 0.5 ms (Tslot=15360·Ts) long.One subframe includes two successive slots. An ith subframe includes2ith and (2i+1)th slots. That is, a radio frame includes 10 subframes. Atime required for transmitting one subframe is defined as a TransmissionTime Interval (TTI). Ts is a sampling time given as Ts=1/(15kHz×2048)=3.2552×10−8 (about 33 ns). One slot includes a plurality ofOrthogonal Frequency Division Multiplexing (OFDM) symbols or SC-FDMAsymbols in the time domain by a plurality of Resource Blocks (RBs) inthe frequency domain.

A slot includes a plurality of OFDM symbols in the time domain. SinceOFDMA is adopted for DL in the 3GPP LTE system, one OFDM symbolrepresents one symbol period. An OFDM symbol may be called an SC-FDMAsymbol or symbol period. An RB is a resource allocation unit including aplurality of contiguous subcarriers in one slot.

In a full FDD system, each of 10 subframes may be used simultaneouslyfor DL transmission and UL transmission during a 10-ms duration. The DLtransmission and the UL transmission are distinguished by frequency. Onthe other hand, a UE cannot perform transmission and receptionsimultaneously in a half FDD system.

The above radio frame structure is purely exemplary. Thus, the number ofsubframes in a radio frame, the number of slots in a subframe, and thenumber of OFDM symbols in a slot may be changed.

FIG. 2B illustrates frame structure type 2. Frame structure type 2 isapplied to a Time Division Duplex (TDD) system. One radio frame is 10 ms(Tf=307200·Ts) long, including two half-frames each having a length of 5ms (=153600·Ts) long. Each half-frame includes five subframes each being1 ms (=30720·Ts) long. An ith subframe includes 2ith and (2i+1)th slotseach having a length of 0.5 ms (Tslot=15360·Ts). Ts is a sampling timegiven as Ts=1/(15 kHz×2048)=3.2552×10−8 (about 33 ns).

A type-2 frame includes a special subframe having three fields, DownlinkPilot Time Slot (DwPTS), Guard Period (GP), and Uplink Pilot Time Slot(UpPTS). The DwPTS is used for initial cell search, synchronization, orchannel estimation at a UE, and the UpPTS is used for channel estimationand UL transmission synchronization with a UE at an base station. The GPis used to cancel UL interference between a UL and a DL, caused by themulti-path delay of a DL signal.

Table 1 below lists special subframe configurations (DwPTS/GP/UpPTSlengths).

TABLE 1 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Special Normal Extended Normal Extended subframecyclic prefix cyclic prefix cyclic prefix cyclic prefix configurationDwPTS in uplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) 2192· T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592· T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — — 9 13168 ·T_(s) — — —

In addition, in the LTE Rel-13 system, it is possible to newly configurethe configuration of special subframes (i.e., the lengths ofDwPTS/GP/UpPTS) by considering the number of additional SC-FDMA symbols,X, which is provided by the higher layer parameter named “srs-UpPtsAdd”(if this parameter is not configured, X is set to 0). In the LTE Rel-14system, specific subframe configuration #10 is newly added. The UE isnot expected to be configured with 2 additional UpPTS SC-FDMA symbolsfor special subframe configurations {3, 4, 7, 8} for normal cyclicprefix in downlink and special subframe configurations {2, 3, 5, 6} forextended cyclic prefix in downlink and 4 additional UpPTS SC-FDMAsymbols for special subframe configurations {1, 2, 3, 4, 6, 7, 8} fornormal cyclic prefix in downlink and special subframe configurations {1,2, 3, 5, 6} for extended cyclic prefix in downlink.)

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Special Normal Extended Normal Extended subframecyclic prefix cyclic prefix cyclic prefix cyclic prefix configurationDwPTS in uplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) (1 +X) · 2192 · T_(s) (1 + X) · 2560 · T_(s)  7680 · T_(s) (1 + X) · 2192 ·T_(s) (1 + X) · 2560 · T_(s) 1 19760 · T_(s) 20480 · T_(s) 2 21952 ·T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600 · T_(s) 4 26336 · T_(s)  7680· T_(s) (2 + X) · 2192 · T_(s) (2 + X) · 2560 · T_(s) 5  6592 · T_(s)(2 + X) · 2192 · T_(s) (2 + X) · 2560 · T_(s) 20480 · T_(s) 6 19760 ·T_(s) 23040 · T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — —9 13168 · T_(s) — — — 10 13168 · T_(s) 13152 · T_(s) 12800 · T_(s) — — —

FIG. 3 illustrates an exemplary structure of a DL resource grid for theduration of one DL slot, which may be used in embodiments of the presentdisclosure.

Referring to FIG. 3, a DL slot includes a plurality of OFDM symbols inthe time domain. One DL slot includes 7 OFDM symbols in the time domainand an RB includes 12 subcarriers in the frequency domain, to which thepresent disclosure is not limited.

Each element of the resource grid is referred to as a Resource Element(RE). An RB includes 12×7 REs. The number of RBs in a DL slot, NDLdepends on a DL transmission bandwidth.

FIG. 4 illustrates a structure of a UL subframe which may be used inembodiments of the present disclosure.

Referring to FIG. 4, a UL subframe may be divided into a control regionand a data region in the frequency domain. A PUCCH carrying UCI isallocated to the control region and a PUSCH carrying user data isallocated to the data region. To maintain a single carrier property, aUE does not transmit a PUCCH and a PUSCH simultaneously. A pair of RBsin a subframe are allocated to a PUCCH for a UE. The RBs of the RB pairoccupy different subcarriers in two slots. Thus it is said that the RBpair frequency-hops over a slot boundary.

FIG. 5 illustrates a structure of a DL subframe that may be used inembodiments of the present disclosure.

Referring to FIG. 5, up to three OFDM symbols of a DL subframe, startingfrom OFDM symbol 0 are used as a control region to which controlchannels are allocated and the other OFDM symbols of the DL subframe areused as a data region to which a PDSCH is allocated. DL control channelsdefined for the 3GPP LTE system include a Physical Control FormatIndicator Channel (PCFICH), a PDCCH, and a Physical Hybrid ARQ IndicatorChannel (PHICH).

The PCFICH is transmitted in the first OFDM symbol of a subframe,carrying information about the number of OFDM symbols used fortransmission of control channels (i.e., the size of the control region)in the subframe. The PHICH is a response channel to a UL transmission,delivering an HARQ ACK/NACK signal. Control information carried on thePDCCH is called Downlink Control Information (DCI). The DCI transportsUL resource assignment information, DL resource assignment information,or UL Transmission (Tx) power control commands for a UE group.

2. New Radio Access Technology System

As a number of communication devices have required higher communicationcapacity, the necessity of the mobile broadband communication muchimproved than the existing radio access technology (RAT) has increased.In addition, massive machine type communications (MTC) capable ofproviding various services at anytime and anywhere by connecting anumber of devices or things to each other has also been required.Moreover, a communication system design capable of supportingservices/UEs sensitive to reliability and latency has been proposed.

As the new RAT considering the enhanced mobile broadband communication,massive MTC, Ultra-reliable and low latency communication (URLLC), andthe like, a new RAT system has been proposed. In the present invention,the corresponding technology is referred to as the new RAT or new radio(NR) for convenience of description.

2.1. Numerologies

The NR system to which the present invention is applicable supportsvarious OFDM numerologies shown in the following table. In this case,the value of P and cyclic prefix information per carrier bandwidth partcan be signaled in DL and UL, respectively. For example, the value of μand cyclic prefix information per downlink carrier bandwidth part may besignaled though DL-BWP-mu and DL-MWP-cp corresponding to higher layersignaling. As another example, the value of μ and cyclic prefixinformation per uplink carrier bandwidth part may be signaled thoughUL-BWP-mu and UL-MWP-cp corresponding to higher layer signaling.

TABLE 3 μ Δf = 2^(μ) · 15 [kHz] Cyclic prefix 0 15 Normal 1 30 Normal 260 Normal, Extended 3 120 Normal 4 240 Normal

2.2 Frame Structure

DL and UL transmission are configured with frames with a length of 10ms. Each frame may be composed of ten subframes, each having a length of1 ms. In this case, the number of consecutive OFDM symbols in eachsubframe is N_(symb) ^(subframe,μ)=N_(symb) ^(slot)N_(slot)^(subframe,μ).

In addition, each subframe may be composed of two half-frames with thesame size. In this case, the two half-frames are composed of subframes 0to 4 and subframes 5 to 9, respectively.

Regarding the subcarrier spacing p, slots may be numbered within onesubframe in ascending order like n_(s) ^(μ)∈{0, . . . N_(slot)^(subframe,μ)−1} and may also be numbered within a frame in ascendingorder like n_(s,f) ^(μ)∈{0, . . . N_(slot) ^(frame,μ)−1}. In this case,the number of consecutive OFDM symbols in one slot (N_(symb) ^(slot))may be determined as shown in the following table according to thecyclic prefix. The start slot (N_(s) ^(μ)) of one subframe is alignedwith the start OFDM symbol (N_(s) ^(μ)N_(symb) ^(slot)) of the samesubframe in the time dimension. Table 4 shows the number of OFDM symbolsin each slot/frame/subframe in the case of the normal cyclic prefix, andTable 5 shows the number of OFDM symbols in each slot/frame/subframe inthe case of the extended cyclic prefix.

TABLE 4 μ N_(symb) ^(slot) N_(slot) ^(frame,μ) N_(slot) ^(subframe,μ) 014 10 1 1 14 20 2 2 14 40 4 3 14 80 8 4 14 160 16 5 14 320 32

TABLE 5 μ N_(symb) ^(slot) N_(slot) ^(frame,μ) N_(slot) ^(subframe,μ) 212 40 4

In the NR system to which the present invention can be applied, aself-contained slot structure can be applied based on theabove-described slot structure.

FIG. 6 is a diagram illustrating a self-contained slot structureapplicable to the present invention.

In FIG. 6, the hatched area (e.g., symbol index=0) indicates a downlinkcontrol region, and the black area (e.g., symbol index=13) indicates anuplink control region. The remaining area (e.g., symbol index=1 to 13)can be used for DL or UL data transmission.

Based on this structure, the base station and UE can sequentiallyperform DL transmission and UL transmission in one slot. That is, thebase station and UE can transmit and receive not only DL data but alsoUL ACK/NACK in response to the DL data in one slot. Consequently, due tosuch a structure, it is possible to reduce a time required until dataretransmission in case a data transmission error occurs, therebyminimizing the latency of the final data transmission.

In this self-contained slot structure, a predetermined length of a timegap is required for the process of allowing the base station and UE toswitch from transmission mode to reception mode and vice versa. To thisend, in the self-contained slot structure, some OFDM symbols at the timeof switching from DL to UL are set as a guard period (GP).

Although it is described that the self-contained slot structure includesboth the DL and UL control regions, these control regions can beselectively included in the self-contained slot structure. In otherwords, the self-contained slot structure according to the presentinvention may include either the DL control region or the UL controlregion as well as both the DL and UL control regions as shown in FIG. 6.

In addition, for example, the slot may have various slot formats. Inthis case, OFDM symbols in each slot can be divided into downlinksymbols (denoted by ‘D’), flexible symbols (denoted by ‘X’), and uplinksymbols (denoted by ‘U’).

Thus, the UE can assume that DL transmission occurs only in symbolsdenoted by ‘D’ and ‘X’ in the DL slot. Similarly, the UE can assume thatUL transmission occurs only in symbols denoted by ‘U’ and ‘X’ in the ULslot.

2.3. Analog Beamforming

In a millimeter wave (mmW) system, since a wavelength is short, aplurality of antenna elements can be installed in the same area. Thatis, considering that the wavelength at 30 GHz band is 1 cm, a total of100 antenna elements can be installed in a 5*5 cm panel at intervals of0.5 lambda (wavelength) in the case of a 2-dimensional array. Therefore,in the mmW system, it is possible to improve the coverage or throughputby increasing the beamforming (BF) gain using multiple antenna elements.

In this case, each antenna element can include a transceiver unit (TXRU)to enable adjustment of transmit power and phase per antenna element. Bydoing so, each antenna element can perform independent beamforming perfrequency resource.

However, installing TXRUs in all of the about 100 antenna elements isless feasible in terms of cost. Therefore, a method of mapping aplurality of antenna elements to one TXRU and adjusting the direction ofa beam using an analog phase shifter has been considered. However, thismethod is disadvantageous in that frequency selective beamforming isimpossible because only one beam direction is generated over the fullband.

To solve this problem, as an intermediate form of digital BF and analogBF, hybrid BF with B TXRUs that are fewer than Q antenna elements can beconsidered. In the case of the hybrid BF, the number of beam directionsthat can be transmitted at the same time is limited to B or less, whichdepends on how B TXRUs and Q antenna elements are connected.

FIGS. 7 and 8 are diagrams illustrating representative methods forconnecting TXRUs to antenna elements. Here, the TXRU virtualizationmodel represents the relationship between TXRU output signals andantenna element output signals.

FIG. 7 shows a method for connecting TXRUs to sub-arrays. In FIG. 7, oneantenna element is connected to one TXRU.

Meanwhile, FIG. 8 shows a method for connecting all TXRUs to all antennaelements. In FIG. 8, all antenna element are connected to all TXRUs. Inthis case, separate addition units are required to connect all antennaelements to all TXRUs as shown in FIG. 8.

In FIGS. 7 and 8, W indicates a phase vector weighted by an analog phaseshifter. That is, W is a major parameter determining the direction ofthe analog beamforming. In this case, the mapping relationship betweenCSI-RS antenna ports and TXRUs may be 1:1 or 1-to-many.

The configuration shown in FIG. 7 has a disadvantage in that it isdifficult to achieve beamforming focusing but has an advantage in thatall antennas can be configured at low cost.

On the contrary, the configuration shown in FIG. 8 is advantageous inthat beamforming focusing can be easily achieved. However, since allantenna elements are connected to the TXRU, it has a disadvantage ofhigh cost.

When a plurality of antennas is used in the NR system to which thepresent invention is applicable, a hybrid beamforming (BF) scheme inwhich digital BF and analog BF are combined may be applied. In thiscase, analog BF (or radio frequency (RF) BF) means an operation ofperforming precoding (or combining) at an RF stage. In hybrid BF, eachof a baseband stage and the RF stage perform precoding (or combining)and, therefore, performance approximating to digital BF can be achievedwhile reducing the number of RF chains and the number of adigital-to-analog (D/A) (or analog-to-digital (A/D) converters.

For convenience of description, a hybrid BF structure may be representedby N transceiver units (TXRUs) and M physical antennas. In this case,digital BF for L data layers to be transmitted by a transmission end maybe represented by an N-by-L matrix. N converted digital signals obtainedthereafter are converted into analog signals via the TXRUs and thensubjected to analog BF, which is represented by an M-by-N matrix.

FIG. 9 is a diagram schematically illustrating an exemplary hybrid BFstructure from the perspective of TXRUs and physical antennas accordingto the present invention. In FIG. 9, the number of digital beams is Land the number analog beams is N.

Additionally, in the NR system to which the present invention isapplicable, an base station designs analog BF to be changed in units ofsymbols to provide more efficient BF support to a UE located in aspecific area. Furthermore, as illustrated in FIG. 9, when N specificTXRUs and M RF antennas are defined as one antenna panel, the NR systemaccording to the present invention considers introducing a plurality ofantenna panels to which independent hybrid BF is applicable.

In the case in which the base station utilizes a plurality of analogbeams as described above, the analog beams advantageous for signalreception may differ according to a UE. Therefore, in the NR system towhich the present invention is applicable, a beam sweeping operation isbeing considered in which the base station transmits signals (at leastsynchronization signals, system information, paging, and the like) byapplying different analog beams in a specific subframe (SF) on asymbol-by-symbol basis so that all UEs may have reception opportunities.

FIG. 10 is a diagram schematically illustrating an exemplary beamsweeping operation for a synchronization signal and system informationin a DL transmission procedure according to the present invention.

In FIG. 10 below, a physical resource (or physical channel) on which thesystem information of the NR system to which the present invention isapplicable is transmitted in a broadcasting manner is referred to as anxPBCH. Here, analog beams belonging to different antenna panels withinone symbol may be simultaneously transmitted.

As illustrated in FIG. 10, in order to measure a channel for each analogbeam in the NR system to which the present invention is applicable,introducing a beam RS (BRS), which is a reference signal (RS)transmitted by applying a single analog beam (corresponding to aspecific antenna panel), is being discussed. The BRS may be defined fora plurality of antenna ports and each antenna port of the BRS maycorrespond to a single analog beam. In this case, unlike the BRS, asynchronization signal or the xPBCH may be transmitted by applying allanalog beams in an analog beam group such that any UE may receive thesignal well.

3. Narrow Band-Internet of Things (NB-IoT)

Hereinafter, the technical features of NB-IoT will be described indetail. While the NB-IoT system based on the 3GPP LTE standard will bemainly described for simplicity, the same configurations is alsoapplicable to the 3GPP NR standard. To this end, some technicalconfigurations may be modified (e.g., subframe→slots)

Although the NB-IoT technology will be described in detail below basedon the LTE standard technology, the LTE standard technology can bereplaced with the NR standard technology within a range easily derivedby those skilled in the art.

3.1. Operation Mode and Frequency

NB-IoT supports three operation modes of in-band, guard band, andstand-alone, and the same requirements apply to each mode.

(1) In the in-band mode, some of the resources in the Long-TermEvolution (LTE) band are allocated to NB-IoT.

(2) In the guard band mode, the guard frequency band of LTE is utilized,and the NB-IoT carrier is disposed as close to the edge subcarrier ofthe LTE as possible.

In the stand-alone mode, some carriers in the Global System for MobileCommunications (GSM) band are separately allocated and operated.

An NB-IoT UE searches for an anchor carrier in units of 100 kHz forinitial synchronization, and the anchor carrier center frequency of thein-band and the guard band should be within ±7.5 kHz from a channelraster of 100 kHz channel. In addition, among the LTE PRBs, 6 middlePRBs are not allocated to NB-IoT. Therefore, the anchor carrier may onlybe positioned on a specific Physical Resource Block (PRB).

FIG. 11 is a diagram schematically illustrating arrangement of anin-band anchor carrier for an LTE bandwidth of 10 MHz.

As shown in FIG. 11, a direct current (DC) subcarrier is positioned at achannel raster. Since the center frequency interval between adjacentPRBs is 180 kHz, PRB indexes 4, 9, 14, 19, 30, 35, 40 and 45 have centerfrequencies at ±2.5 kH from the channel raster.

Similarly, the center frequency of a PRB suitable for anchor carriertransmission is positioned at ±2.5 kHz from the channel raster in thecase of a bandwidth of 20 MHz, and is positioned at ±7.5 kHz forbandwidths of 3 MHz, 5 MHz and 15 MHz.

In the guard band mode, the PRB immediately adjacent to the edge PRB ofLTE is positioned at ±2.5 kHz from the channel raster in the case of thebandwidths of 10 MHz and 20 MHz. In the case of 3 MHz, 5 MHz, and 15MHz, the center frequency of the anchor carrier may be positioned at±7.5 kHz from the channel raster by using the guard frequency bandcorresponding to the three subcarriers from the edge PRB.

The stand-alone mode anchor carriers are aligned with a 100-kHz channelraster, and all GSM carriers, including DC carriers, may be used asNB-IoT anchor carriers.

In addition, the NB-IoT supports operation of multiple carriers, andcombinations of in-band+in-band, in-band+guard band, guard band+guardband, and stand-alone+stand-alone may be used.

3.2. Physical Channel 3.2.1. Downlink (DL)

For the NB-IoT downlink, an Orthogonal Frequency Division MultipleAccess (OFDMA) scheme with a 15 kHz subcarrier spacing is employed. Thisscheme provides orthogonality between subcarriers to facilitatecoexistence with LTE systems.

On the downlink, physical channels such as a narrowband physicalbroadcast channel (NPBCH), a narrowband physical downlink shared channel(NPDSCH), and a narrowband physical downlink control channel (NPDCCH)are provided, and a narrowband secondary synchronization signal (NPSS),a narrowband primary synchronization signal (NSSS) and a narrowbandreference signal (NRS) are provided as physical signals.

FIG. 12 is a diagram schematically illustrating positions where aphysical downlink channel and a downlink signal are transmitted in anFDD LTE system.

As shown in FIG. 12, the NPBCH is transmitted in the first subframe ofeach frame, the NPSS is transmitted in the sixth subframe of each frame,and the NSSS is transmitted in the last subframe of each even-numberedframe.

The NB-IoT UE should acquire system information about a cell in order toaccess a network. To this end, synchronization with the cell should beobtained through a cell search procedure, and synchronization signals(NPSS, NSSS) are transmitted on the downlink for this purpose.

The NB-IoT UE acquires frequency, symbol, and frame synchronizationusing the synchronization signals and searches for 504 Physical Cell IDs(PCIDs). The LTE synchronization signal is designed to be transmittedover 6 PRB resources and is not reusable for NB-IoT, which uses 1 PRB.

Thus, a new NB-IoT synchronization signal has been designed and is tothe three operation modes of NB-IoT in the same manner.

More specifically, the NPSS, which is a synchronization signal in theNB-IoT system, is composed of a Zadoff-Chu (ZC) sequence having asequence length of 11 and a root index value of 5.

Here, the NPSS may be generated according to the following equation.

$\begin{matrix}{{{d_{l}(n)} = {{S(l)} \cdot e^{{- j}\frac{\pi\; u\;{n{({n + 1})}}}{11}}}},{n = 0},1,\ldots\;,10} & {{Equation}\mspace{14mu} 1}\end{matrix}$

Here, S(1) for symbol index 1 may be defined as shown in the followingtable.

TABLE 6 Cyclic prefix length S(3), . . . ,S(13) Normal 1 1 1 1 −1 −1 1 11 −1 1

The NSSS, which is a synchronization signal in the NB-IoT system, iscomposed of a combination of a ZC sequence having a sequence length of131 and a binary scrambling sequence such as a Hadamard sequence. Inparticular, the NSSS indicates a PCID to the NB-IoT UEs in the cellthrough the combination of the sequences.

Here, the NSSS may be generated according to the following equation.

$\begin{matrix}{{d(n)} = {{b_{q}(m)}e^{{- j}\; 2\;\pi\;\theta_{f}n}e^{{- j}\frac{\pi\;{{un}^{\prime}{({n^{\prime} + 1})}}}{131}}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

Here, the parameters in Equation 2 may be defined as follows.

TABLE 7 n = 0,1, . . . ,131 n′ = nmod131 m = nmod128 u = N_(ID)^(Ncell)mod126 + 3$q = \left\lfloor \frac{N_{ID}^{Ncell}}{126} \right\rfloor$

The binary sequence b_(q)(m) may be defined as shown in the followingtable, and the cyclic shift θ_(f) for the frame number n_(f) may bedefined by the equation given below.

TABLE 8 q b_(q) (0), . . . , b_(q) (127) 0 [1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1] 1 [1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1−1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1−1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1−1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1−1 −1 1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1] 2 [1 −1 −1 1 −1 1 1 −1−1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1−1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 1 −1−1 1 −1 1 1 −1 −1 1 1 −1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1−1 1 1 −1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1−1 1] 3 [1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 1−1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 −1 11 −1 −1 1 1 −1 1 −1 −1 1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 −1 1 1 −1 1 −1 −1 1−1 1 1 −1 −1 1 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1 −1 1 1 −1 1 −1 −1 1 −11 1 −1 1 −1 −1 1 1 −1 −1 1 −1 1 1 −1]

$\begin{matrix}{\theta_{f} = {\frac{33}{132}\left( {n_{f}/2} \right){mod}\mspace{11mu} 4}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

The NRS is provided as a reference signal for channel estimationnecessary for physical downlink channel demodulation and is generated inthe same manner as in LTE. However, NBNarrowband-Physical Cell ID (PCID)is used as the initial value for initialization.

The NRS is transmitted to one or two antenna ports, and up to two basestation transmit antennas of NB-IoT are supported.

The NPBCH carries the Master Information Block-Narrowband (MIB-NB),which is the minimum system information that the NB-IoT UE should knowto access the system, to the UE.

The transport block size (TBS) of the MIB-NB, which is 34 bits, isupdated and transmitted with a periodicity of transmission time interval(TTIs) of 640 ms, and includes information such as the operation mode,the system frame number (SFN), the hyper-SFN, the cell-specificreference signal (CRS) port number, and the channel raster offset.

The NPBCH signal may be repeatedly transmitted 8 times in total toimprove coverage.

The NPDCCH has the same transmit antenna configuration as the NPBCH, andsupports three types of downlink control information (DCI) formats. DCINO is used to transmit the scheduling information of the narrowbandphysical uplink shared channel (NPUSCH) to the UE, and DCIs N1 and N2are used in transmitting information required for demodulation of theNPDSCH to the UE. Transmission of the NPDCCH may be repeated up to 2048times to improve coverage.

The NPDSCH is a physical channel for transmission of a transport channel(TrCH) such as the downlink-shared channel (DL-SCH) or the pagingchannel (PCH). The maximum TBS is 680 bits and transmission may berepeated up to 2048 times to improve coverage.

3.2.2. Uplink (UL)

The uplink physical channels include a narrowband physical random accesschannel (NPRACH) and the NPUSCH, and support single-tone transmissionand multi-tone transmission.

Multi-tone transmission is only supported for subcarrier spacing of 15kHz, and single-tone transmission is supported for subcarrier spacingsof 3.5 kHz and 15 kHz.

On the uplink, the 15-Hz subcarrier spacing may maintain theorthogonality with the LTE, thereby providing the optimum performance.However, the 3.75-kHz subcarrier spacing may degrade the orthogonality,resulting in performance degradation due to interference.

The NPRACH preamble consists of four symbol groups, wherein each of thesymbol groups consists of a cyclic prefix (CP) and five symbols. TheNPRACH only supports single-tone transmission with 3.75-kHz subcarrierspacing and provides CPs having lengths of 66.7 μs and 266.67 μs tosupport different cell radii. Each symbol group performs frequencyhopping and the hopping pattern is as follows.

The subcarrier for transmitting the first symbol group is determined ina pseudo-random manner. The second symbol group hops by one subcarrier,the third symbol group hops by six subcarriers, and the fourth symbolgroup hops by one subcarrier hop.

In the case of repeated transmission, the frequency hopping procedure isrepeatedly applied. In order to improve the coverage, the NPRACHpreamble may be repeatedly transmitted up to 128 times.

The NPUSCH supports two formats. Format 1 is for UL-SCH transmission,and the maximum transmission block size (TBS) thereof is 1000 bits.Format 2 is used for transmission of uplink control information such asHARQ ACK signaling. Format 1 supports single-tone transmission andmulti-tone transmission, and Format 2 supports only single-tonetransmission. In single-tone transmission, p/2-binary phase shift keying(BPSK) and p/4-QPSK (quadrature phase shift keying) are used to reducethe peak-to-average power ratio (PAPR).

3.2.3. Resource Mapping

In the stand-alone and guard band modes, all resources included in 1 PRBmay be allocated to the NB-IoT. However, in the in-band mode, resourcemapping is limited in order to maintain orthogonality with the existingLTE signals.

The NB-IoT UE should detect NPSS and NSSS for initial synchronization inthe absence of system information. Accordingly, resources (OFDM symbols0 to 2 in each subframe) classified as the LTE control channelallocation region cannot be allocated to the NPSS and NSSS, and NPSS andNSSS symbols mapped to a resource element (RE) overlapping with the LTECRS should be punctured.

FIG. 13 is a diagram illustrating exemplary resource allocation of anNB-IoT signal and an LTE signal in an in-band mode.

As shown in FIG. 13, for ease of implementation, the NPSS and NSSS arenot transmitted on the first three OFDM symbols in the subframecorresponding to the transmission resource region for the controlchannel in the conventional LTE system regardless of the operation mode.REs for the common reference signal (CRS) in the conventional LTE systemand the NPSS/NSSS colliding on a physical resource are punctured andmapped so as not to affect the conventional LTE system.

After the cell search, the NB-IoT UE demodulates the NPBCH in theabsence of system information other than the PCID. Therefore, the NPBCHsymbol cannot be mapped to the LTE control channel allocation region.Since four LTE antenna ports and two NB-IoT antenna ports should beassumed, the REs allocated to the CRS and NRS cannot be allocated to theNPBCH. Therefore, the NPBCH should be rate-matched according to thegiven available resources.

After demodulating the NPBCH, the NB-IoT UE may acquire informationabout the CRS antenna port number, but still may not know theinformation about the LTE control channel allocation region. Therefore,NPDSCH for transmitting System Information Block type 1 (SIB1) data isnot mapped to resources classified as the LTE control channel allocationregion.

However, unlike the case of the NPBCH, an RE not allocated to the LTECRS may be allocated to the NPDSCH. Since the NB-IoT UE has acquired allthe information related to resource mapping after receiving SIB1, theNPDSCH (except for the case where SIB1 is transmitted) and the NPDCCHmay be mapped to available resources based on the LTE control channelinformation and the CRS antenna port number.

4. Proposed Embodiments

Hereinafter, the present invention will be described in more detailbased on the technical ideas disclosed above.

The NB-IoT in the conventional LTE system is designed to be supportableonly in the normal cyclic prefix (CP) of the frequency division duplex(FDD) system. For anchor-carriers on which the synchronization signals(e.g., the narrowband primary synchronization signal (NPSS), thenarrowband secondary synchronization signal (NSSS), the masterinformation block-narrow band (MIB-NB), and system information blocktype1-nb (SIB1-NB)) are transmitted, the transmission subframe positionfor each channel is fixed in the time domain as shown in the table givenbelow.

TABLE 9 Subframe number 0 1 2 3 4 5 6 7 8 9 Even-numbered NPBCH SIB1-NPSS NSSS radio frame NB Odd-numbered NPBCH SIB1- NPSS radio frame NB

Here, the NPSS and NPBCH are transmitted in subframes 0 and 5 of eachradio frame, respectively, while the NSSS is transmitted only insubframe 9 of an even-numbered radio frame. In addition, SIB1-NB(SystemInformationBlockType1-NB) may be transmitted over subframe 4 inevery other frame within 16 consecutive radio frames, wherein the periodand start position of the 16 radio frames may vary according to N_(ID)^(Ncell) and schedulingInfoSIB1. However, even if subframes are not usedfor SIB-1NB transmission in a specific cell, SIB1-NB transmission may beperformed in subframe 4 in another cell.

Therefore, it is required to transmit at least 4 DL subframes on theanchor-carrier for the NB-IoT service, and at least 5 DL subframesshould be secured for the random access response and theCarrierConfigDedicated-NB transmission for the non-anchor carrierconfiguration.

On the other hand, in the TDD system, the number of DL subframes in aradio frame may be limited according to the UL/DL configuration, asshown in the table below.

TABLE 10 Downlink-to-Uplink Uplink-downlink Switch-point Subframe numberconfiguration periodicity 0 1 2 3 4 5 6 7 8 9 0  5 ms D S U U U D S U UU 1  5 ms D S U U D D S U U D 2  5 ms D S U D D D S U D D 3 10 ms D S UU U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D D D D 6 5 ms D S U U U D S U U D

Here, D, U, and S denote downlink, uplink, and special subframe,respectively. For an eNB for which the Enhanced Interference Mitigation& Traffic Adaptation (eIMTA) feature is supported, a part of the ULsubframes may be dynamically changed to DL subframes.

The DwPTS and the UpPTS are configured before and after a specialsubframe that is present between DL and UL intervals, respectively. Thegap between the DwPTS and the UpPTS is used for downlink-to-uplinkswitching and timing advanced (TA). As described above, theconfiguration of the OFDM or SC-FDMA symbol level in the specialsubframe may be represented as shown in FIGS. 14 to 17 according to theCP length of the downlink and uplink and the higher layer parametersrs-UpPtsAdd. Here, as described above, X (srs-UpPtsAdd) may not be setto 2 for special subframe configurations {3, 4, 7, 8} for normal CP indownlink and special subframe configurations {2, 3, 5, 6} for extendedCP in downlink. In addition, X (srs-UpPtsAdd) may not be set to 4 forspecial subframe configurations {1, 2, 3, 4, 6, 7, 8} for normal CP indownlink and special subframe configurations {1, 2, 3, 5, 6} forextended CP in downlink.

FIG. 14 is a diagram illustrating special subframe configurations towhich normal CP in DL and normal CP in UL are applied.

FIG. 15 is a diagram illustrating special subframe configurations towhich normal CP in DL and extended CP in UL are applied.

FIG. 16 is a diagram illustrating special subframe configurations towhich extended CP in DL and normal CP in UL are applied.

FIG. 17 is a diagram illustrating special subframe configurations towhich extended CP in DL and extended CP in UL are applied.

FIG. 18 is a diagram illustrating subframe configuration and the meaningof notations according to the CP length in FIGS. 14 to 17. As shown inFIG. 18, a subframe according to extended CP is composed of 12 symbols,and a subframe according to normal CP is composed of 14 symbols. Here,each DL symbol and UL symbol may be represented as shown at the bottomin FIG. 18. Hereinafter, it is assumed that the same structure asdescribed above is applied to the present invention.

Here, it is assumed that the n-th downlink/uplink symbol of DwPTS/UpPTSand the index n of an additional downlink/uplink symbol conform to theindex numbers of FIG. 18 for convenience of explanation and expression.That is, in each configuration, the starting index of n_U may not be 0.

In FIGS. 14 to 17, the null period of the DwPTS and UpPTS periods may beused as a DL-to-UL switching gap by the UE (e.g., the NB-IoT UE), andmay be configured as about 20 usec, which is about 1/3 times shorterthan the periodicity of the OFDM or SC-FDMA symbol.

Also, n-A (x, y) in each row represents the default type of the n-thspecial subframe configuration having DwPTS and UpPTS periods includingx and y OFDM and SC-FDMA symbols, and n-B (x,y+2) and n-C(x,y+4)represent special subframe configurations in which the number of SC-FDMAsymbols is increased from the default type n-A (x, y) according to thevalue of X (srs-UpPtsAdd).

As described above, in the TDD system, the number of subframes fixed todownlink may vary according to the UL/DL configuration, and even thenumber of OFDM symbols fixed to downlink in the special subframe mayvary according to the special subframe configuration.

However, when the eIMTA feature is supported, the eNB may be allowed todynamically change a part of the uplink subframes to downlink subframes.

However, considering the fixed scheduling of NPSS, NSSS, NPBCH, andSIB1-NB of the NB-IoT system, the eIMTA scheme in which a specificuplink subframe is always changed to a downlink subframe may not bedesirable.

Therefore, in order to support NB-IoT in the TDD system, it is necessaryto design a structure capable of supporting available downlink subframesor OFDM symbols as many as possible according to a combination ofvarious UL/DL configurations and special subframe configurations.

To design an NB-IoT anchor-carrier structure suitable for the TDDsystem, the following items or constraints may be considered.

1. Operation Mode

NB-IoT supports four operation modes (In-band SamePCI, In-bandDifferentPCI, guard band, standalone). The operation mode of ananchor-carrier is transmitted in the MIB-NB of the NPBCH. Accordingly,an NB-NB-IoT channel structure in which the NB-IoT UE can perform thesame synchronization regardless of the operation mode until detectionand decoding of the NPSS, NSSS and NPBCH of the NB-IoT UE needs to beprovided. Otherwise, the NB-IoT UE needs to add blind detection anddecoding according to the operation mode. This structure is not suitablefor the NB-IoT modem, which has a feature of “low cost and long batterylife.”

2. UL/DL Configuration and Special Subframe Configuration

As can be seen from Table 10, subframe 0 and subframe 5 are downlinksubframes available to all UL/DL configurations in common. Subframe 1may always be configured as a partial downlink subframe, and subframe 6may be configured as a partial downlink subframe or a fulldownlinksubframe (a subframe in which all symbols are configured for downlinkOFDM) according to the UL/DL configuration.

Therefore, in order to support NB-IoT in all UL/DL configurations, onlysubframes 0 and 5 may be used as full downlink subframes.

On the other hand, when another NB-IoT channel structure is designedaccording to the UL/DL configuration and the special subframeconfiguration to secure another downlink subframe or OFDM symbol as afull downlink subframe, blind detection and decoding may be added. Thisstructure is not suitable for the NB-IoT modem featuring “low cost andlong battery life.”

3. Reuse of NPSS and NSSS of LTE Rel.14

As described above, NPSS and NSSS are defined in the 3GPP standard.

More specifically, the NPSS includes a Zadoff-Chu sequence and a coversequence of Table 4, and is allocated to 11 OFDM symbols except for thefirst 3 OFDM symbols of the subframe for transmission.

The NSSS is additionally subjected to phase rotation according to thebinary sequence and frame number of Table 8 based on the Zadoff-Chusequence, and then allocated to 11 OFDM symbols except for the firstthree OFDM symbols of the subframe as in the case of the NPSS so as tobe transmitted.

In other words, in order to allocate the NPSS and NSSS, one PRB pairhaving 12 resource elements (REs) is required in the frequency domain,and 12 OFDM symbols are required in the time domain. In addition, theNPSS and NSSS may be positioned on the consecutive OFDM symbols so as toassume that there is a little change in channel in each sequence in thetime domain. If some symbols in each sequence are arrangednon-consecutively in the time domain, decoding performance may bedegraded.

Therefore, even in NB-IoT of the TDD system, the NPSS and NSSS need tobe allocated to at least 11 consecutive OFDM symbols in the time domain.

4. Re-Use of NPBCH of LTE Rel. 14

The NPBCH is transmitted on 11 consecutive OFDM symbols in everysubframe 0. However, unlike the NPSS and NSSS, MIB-NB, which has apayload of 34 bits (with space of 11 bits) and cyclic redundancy check(CRC) of 16 bits is subjected to 1/3 tail-biting convolutional code(TBCC) encoding and rate matching and is then subjected to QPSKmodulation so as to be transmitted for 640 msec.

Then, the NPBCH may be demodulated and decoded through narrow bandreference signal (NRS)-based channel estimation.

Therefore, unlike the NPSS and NSSS, the NPBCH does not need to have 11consecutive OFDM symbols in the time domain. Even when it is transmittedon non-consecutive OFDM symbols, and may be designed by changing theexisting structure only if the NRS four channel estimation is includedin the non-consecutive OFDM symbol interval.

However, in order to support the same modulation ordering (QPSK) andcode rate as those of the existing NPBCH, it needs to be allocated to 11OFDM symbols in the radio frame, or 100 REs are required except for CRSREs of 4 ports and NRS REs of 2 ports.

In this case, if different PBCH structures are designed according to theoperation mode and the UL/DL configuration, they may not be suitable forthe NB-IoT modem which has a feature of “low cost and long battery life”from the perspective of the NB-IoT UE because blind detection anddecoding are added.

In the present invention, based on the considerations and constraintsdescribed above, a detailed description will be given of the structuresand arrangement of synchronization signals (NPSS and NSSS), channels(NPBCH), NRS-B (which is a reference signal for PBCH demodulation andmay be different from NPDCCH and/or NRS of NPDSCH), and SIB1-NB for theTDD system, and a signal transmission/reception method based thereon.

4.1. First Proposal: “Designate the Default Carrier for NPBCH andSIB1-NB

In this section, as a way to support NB-IoT operation in all UL/DLconfigurations, an arrangement structure in which the NPSS and NSSS orthe NSSS and NPSS are transmitted and received in subframe 0 andsubframe 5 based on UL/DL configuration 0, which has the smallest numberof downlink subframes. Here, the subject transmitting the NPSS and/orthe NSSS may be an eNB, and the subject receiving the NPSS and/or theNSSS may be an NB-IoT UE.

Here, because the full downlink subframes in which the NPBCH and theSIB1-NB can be transmitted may be insufficient, the NPBCH and theSIB1-NB may be transmitted on a non-anchor carrier in the presentinvention.

However, as the non-anchor carrier operation is defined as thecapability of a UE, there may be a case where non-anchor configurationis not possible depending on the capability of the UE. Whenconfiguration is established so as not to support UL/DL configuration 0particularly for a NB-IoT UE for which only the single-carrier operationis supported, ambiguity may occur for the NB-IoT UE because the UL/DLconfiguration is not recognizable using sequence information about theNPSS and NSSS alone. Thereby, it is difficult for the eNB to expect thecorrect operation of the NB-IoT UE.

Therefore, in order to support the NB-IoT operation in all TDD UL/DLconfigurations, it is necessary to assume that the non-anchor carrieroperation of the UE is mandatory. In this case, the TDD NB-IoT UE maydetect the NPSS and NSS on the anchor-carrier, change the frequency to aspecific default carrier, and expect NPBCH and SIB1-NB to be received onthe non-anchor carrier.

Here, the default non-anchor carrier on which NPBCH and SIB1-NB can betransmitted (and random access can be performed), may be referred to asa second-anchor carrier. This operation may be pre-defined by anequation representing a relationship between the anchor-carrier and thesecond-anchor carrier using a similar method to E-UTRA Absolute RadioFrequency Channel Number (EARFCN) or may be pre-defined as a specificoffset value. Here, the method similar to EARFCN may be defined as thefollowing equation.F _(UL) −F _(DL_low)+0.1(N _(DL) −N _(Offs,DL))+0.0025(2M _(DL)+1)+f(M_(DL))[MHz]  Equation 4

Here, F_(UL) and F_(DL_low) denote the second-anchor carrier frequencyand the lowest frequency (constant) of the corresponding band,respectively, and N_(DL), N_(Offs,DL), and M_(DL) denote the downlinkEARFCN number, an offset value for calculation of the downlink EARFCN,and the downlink channel number of NB-IoT. In addition, f(M_(DL))denotes a function indicating the relative offset between theanchor-carrier and the second-anchor carrier and may have a valuegreater than or equal to 0. f(M_(DL)) be set to be band-agnostic or bandnon-agnostic, and the values thereof may be limited in consideration of3 MHz, which is the minimum LTE bandwidth in which the NB-IoT operationcan be performed. In other words, only PRB 2 or 12 is allowed to be usedas the anchor carrier at 3 MHz, and the assignable second-anchor carriermay be set to one of 8 values except for either center 6 RBs or theanchor-carrier.

The NPSS, NSSS, and NPBCH may be configured to be transmitted on theanchor-carrier, and only SIB1-NB may be configured to be transmitted onthe second-anchor carrier. This configuration may be applied even to acase where NB-IoT is not supported in UL-DL configuration 0. In thiscase, the parameters of f(M_(DL)) may be allocated to the information ofthe 11 spare bits in addition to schedulingInfoSIB1-r13 of the MIB-NBand provided to the NB-IoT UE.

4.2. Second Proposal: “Use the Same Subframe Positions as in thePrevious Cases for NPSS, NSSS, and NPBCH, and Vary the Position ofSIB1-NB According to UL/DL Configurations (Part A)”

In this section, a detail description will be given of a method ofvarying the subframe position of SIB1-NB according to the UL/DLconfiguration while maintaining the same structure of NPSS, NSSS andNPBCH as the previous cases, assuming that NB-IoT is not supported inUL/DL configuration 0.

However, since the subframe position of SIB1-NB is not fixed,information about scheduling of SIB1-NB may be added to and transmittedin MIB-NB.

According to the method proposed in this section, the subframe positionsof the NPSS, NSSS, NPBCH, and SIB1-NB may be configured as shown in thefollowing two tables. Alternatively, SIB1-NB and NSSS may be transmittedin subframe 9 alternately every 10 msec.

TABLE 11 Subframe number 0 1 2 3 4 5 6 7 8 9 UL/DL 0 D S U U U D S U U Uconfiguration NPBCH NPSS 1 D S U U D D S U U D NPBCH SIB1-NB NPSS NSSS 2D S U D D D S U D D NPBCH SIB1-NB NPSS NSSS 3 D S U U U D D D D D NPBCHNPSS SIB1-NB NSSS 4 D S U U D D D D D D NPBCH SIB1-NB NPSS NSSS 5 D S UD D D D D D D NPBCH SIB1-NB NPSS NSSS 6 D S U U U D S U U D NPBCHSIB1-NB-A NPSS SIB1-NB-B NSSS

TABLE 12 Subframe number 0 1 2 3 4 5 6 7 8 9 UL/DL 0 D S U U U D S U U Uconfiguration NPBCH NPSS 1 D S U U D D S U U D NPBCH SIB1-NB NPSS NSSS 2D S U D D D S U D D NPBCH SIB1-NB NPSS NSSS 3 D S U U U D D D D D NPBCHNPSS SIB1-NB NSSS 4 D S U U D D D D D D NPBCH NPSS SIB1-NB NSSS 5 D S UD D D D D D D NPBCH NPSS SIB1-NB NSSS 6 D S U U U D S U U D NPBCHSIB1-NB-A NPSS SIB1-NB-B NSSS

Here, the NSSS is transmitted only in subframe 9 of an even-numberedradio frame. In this case, since UL/DL configuration 0 has only twofulldownlink subframes in the radio frame, it is assumed that UL/DLconfiguration 0 is not considered in the second proposal.

In addition, UL/DL configuration 6 has only three fulldownlink subframesin the radio frame. Accordingly, in UL/DL configuration 6, SIB1-NB maybe divided into SIB1-NB-A and SIB1-NB-B and transmitted using the DwPTSof special subframes 1 and 6, or may be transmitted through only one ofspecial subframes 1 and 6. This method may be considered particularly inthe NB-IoT system according to the 3GPP NR system.

As a method to vary the scheduling of SIB1-NB according to the UL/DLconfiguration and special subframe configurations, SIB1-NB schedulinginformation needs to be changed in or added to MIB-NB and transmitted.

Information for SIB1-NB scheduling may be included in the MIB as 4-bitinformation and transmitted to the NB-IoT UE. The 4-bit information ofthe MIB may determine the repetition number and TB S of the SIB1-NB andbe transmitted by being modulated through quadrature phase shift keying(QPSK).

Then, the NB-IoT UE uses 11 OFDM symbols except for the first 3 OFDMsymbols in the radio frame, and performs rate matching based on theNB-IoT antenna port information and LTE antenna port informationobtained from NPBCH detection. In particular, the NB-IoT UE maydetermine the position of the radio frame in which the SIB1-NB istransmitted, based on the SIB1-NB repetition information obtained fromthe MIB-NB and N_(ID) ^(Ncell) obtained from the NSSS.

The NB-IoT UE may use “a part of the 11 spare bits for the NPBCH” or “aCRC mask different from the conventional NPBCH CRC masking” to acquirethe information about the subframe position of the SIB1-NB.

Here, according to the method of “using a part of the 11 spare bits forthe NPBCH”, up to 2048 pieces of information can be distinguished fromeach other. However, since there is a possibility that the spare bitswill be used for indication of other information in the future, aminimum number of bits may be allocated to information about thesubframe position of the SIB1-NB.

According to the method of “using a CRC mask different from theconventional NPBCH CRC masking,” performance of the CRC false alarm maybe affected by the amount of added information. Accordingly, theinformation about the SIB1-NB needs to be distinguished at the minimumlevel. In this case, the information about the SIB1-NB may bedistinguished in each case as follows.

1. When the Position of SIB1-NB is Fixed According to UL/DLConfigurations

Referring to Table 11, SIB1-NB may be transmitted in (over) subframe 4or 9 or subframe 1 or 6 (or 1 and 6). Accordingly, the information aboutthe subframe position of SIB1-NB may be divided into a maximum of four(or five) pieces.

2. When the Position of SIB1-NB Changes According to UL/DLConfigurations

Referring to Table 12, SIB1-NB may be transmitted in (over) subframe 3,4, 6, 7, 8, or 1 (or subframes 1 and 6). In this case, the informationabout the subframe position of SIB1-NB may be divided into a maximum ofsix (or seven) pieces.

3. When the Position of SIB1-NB Changes According to Special SubframeConfigurations

Referring to Tables 11 and 12, in the case of UL/DL configuration 6,NPSS, NSSS, and NPBCH are allocated to the fulldownlink subframes, andaccordingly SIB1-NB may be allocated to subframe 1 or 6 (or subframes 1and 6), which are special subframes.

In this case, the DwPTS period varies among the special subframeconfigurations. Thereby, the number of available OFDMs may be limited.Further, because the number of OFDM symbols in the control region is notknown until the NB-IoT UE decodes SIB1-NB, the number of OFDM symbols onwhich SIB1-NB can be transmitted except for 3 OFDM symbols in the DwPTSperiod may be further reduced.

Accordingly, to use as many OFDM symbols as possible in the DwPTSperiod, the eNB may transmit, to the NB-IoT UE, information about “thenumber of symbols of the control region of the SIB1-NB subframes on theNPBCH.”

In addition, there are 10 special subframe configurations for normal CPand types and 8 special subframe configurations for extended CP.However, in distinguishing only information about the DwPTS period, 6special subframe configurations are enough for normal CP and 5 specialsubframe configurations are enough for extended CP.

Further, if the number of downlink OFDM symbols of the DwPTS isinsufficient, a downlink OFDM symbol may be further allocated in the gapperiod subsequent to the DwPTS to transmit the SIB1-NB. In this case, alegacy LTE reference signal (e.g., CRS) may not be included in thedownlink OFDM symbol added after the DwPTS period. As a result, ratematching for SIB1-NB may be applied differently from the existing DwPTSor fulldownlink subframes.

Alternatively, SIB1-NB and NSSS may be transmitted in subframe 9alternately every 10 msec.

4.3. Third Proposal: “Use the Same Subframe Positions as in the PreviousCases for NPSS, NSSS, and NPBCH, and Vary the Position of SIB1-NBAccording to UL/DL Configurations (Part B)”

In this section, a method which is similar to the second proposal andallows even UL/DL configuration 0 to be used will be described indetail.

The proposed method, however, may be applied only to the eNB supportingthe eIMTA or the eNB allowing the scheduling constraint on subframe 9.According, uplink subframe 9 may be changed to a downlink subframe every2 msec as shown in the table below.

In addition, the SIB1-NB may be divided into two parts as in UL/DLsubframe configuration 6 and transmitted in subframes 1 and 6.

Alternatively, the SIB1-NB and NSSS may be transmitted in subframe 9alternately every 10 msec.

TABLE 13 Subframe number 0 1 2 3 4 5 6 7 8 9 UL/DL 0 D S U U U D S U U Uor D configuration NPBCH SIB1-NB-A NPSS SIB1-NB-B NSSS 1 D S U U D D S UU D NPBCH SIB1-NB NPSS NSSS 2 D S U D D D S U D D NPBCH SIB1-NB NPSSNSSS 3 D S U U U D D D D D NPBCH NPSS SIB1-NB NSSS 4 D S U U D D D D D DNPBCH SIB1-NB NPSS NSSS 5 D S U D D D D D D D NPBCH SIB1-NB NPSS NSSS 6D S U U U D S U U D NPBCH SIB1-NB-A NPSS SIB1-NB-B NSSS

4.4. Fourth Proposal: “Transmit NPBCH in a Special Subframe of theAnchor Carrier”

As described above, the NPBCH is transmitted through QPSK modulationunlike NPSS and NSSS, which are composed of a combination of specificsequences, and accordingly the NPBCH may not need to be transmitted onconsecutive OFDM symbols. However, in this case, an NRS for channelestimation may be transmitted within the interval of non-consecutiveOFDM symbols. Further, considering that the TDD system is generallysuitable for relatively narrow coverage compared to the FDD system, thecode rate of the NPBCH may be designed to be higher than that of theNPBCH of LTE Rel.14 NB-IoT. In other words, in the TDD system, a newNPBCH channel structure or allocation method using a smaller number ofOFDM symbols than the NPBCH of LTE Rel. 14 may be considered.

TABLE 14 Subframe number 0 1 2 3 4 5 6 7 8 9 UL/DL 0 D S U U U D S U U Uconfiguration NPSS NPBCH-A NSSS NPBCH-B 1 D S U U D D S U U D NPSSNPBCH-A NSSS NPBCH-B 2 D S U D D D S U D D NPSS NPBCH-A NSSS NPBCH-B 3 DS U U U D D D D D NPSS NPBCH-A NSSS NPBCH-B 4 D S U U D D D D D D NPSSNPBCH-A NSSS NPBCH-B 5 D S U D D D D D D D NPSS NPBCH-A NSSS NPBCH-B 6 DS U U U D S U U D NPSS NPBCH-A NSSS NPBCH-B

Table 14 shows an example in which NPSS, NSSS, and NPBCH are transmittedon the anchor-carrier in all UL/DL configurations. In this case, SIB1-NBmay be transmitted on the second-anchor carrier as in the firstproposal.

Subframes 0 and 5 are configured as fulldownlink subframes for all UL/DLconfigurations. Accordingly, the NPSS and NSSS may be transmitted insubframes 0 and 5, respectively, or may be transmitted in subframes 5annual 0, respectively.

The NPBCH, which is modulated through QPSK and transmitted, may bedivided into part-A and part-B as shown in Table 13 and transmitted insubframes 1 and 6. Alternatively, the payload size of the MIB may bereduced or the code rate may be increased to transmit the NPBCH in onlyone of subframe 1 or 6.

In the following description, it is assumed that the NPBCH is dividedinto part-A and part-B and transmitted.

In UL/DL configuration 3, 4, and 5, subframe 6 is configured as afulldownlink subframe. However, in order to design the NPBCH structureirrespective of the UL/DL configurations, the NPBCH may be divided intopart-A and part-B even in UL/DL configurations 3, 4, and 5 in the samemanner as in the other UL/DL configurations.

If the NPBCH is configured to be transmitted only in subframe 6 in thecase of UL/DL configurations 3, 4, and 5 without being divided intopart-A and part-B, a method of “using a part of the 11 spare bits forthe NPBCH” or “extending the table of NPBCH CRC masking” may be used todistinguish such configuration from NPBCH configurations for the otherUL/DL subframes.

In order to divide the NPBCH into part-A and part-B to transmit NPBCH-Aand NPBCH-B in the DwPTS of special subframes, the NB-IoT UE needsinformation about a DwPTS period for rate matching. Thus, in a mannersimilar to the second proposal described above, the eNB may providerelated information to the NB-IoT UE by “using a part of the 11 sparebits for the NPBCH” or “extending the table of NPBCH CRC masking.”

Alternatively, the SIB1-NB and NSSS may be transmitted in subframe 9alternately every 10 msec.

4.5. Fifth Proposal: “Transmit NSSS and SIB1-NB Through TimeMultiplexing”

Unlike the NPSS and NPBCH, the NSSS and SIB1-NB may not be transmittedin every radio frame. More specifically, the NSSS may be configured tobe transmitted once every 2 msec, and the SIB1-NB may be configured tobe transmitted once every 2 msec or not to be transmitted for severalmsec according to the repetition number and N_(ID) ^(Ncell).

Hereinafter, a method of time-multiplexing NSSS and SIB1-NB on a radioframe basis will be described in detail based on the features of theNSSS and SIB1-NB whose discontinuous transmission is allowed asdescribed above.

The described time multiplexing method may be defined separately fromthe subframe positions of the NPSS and NPBCH, and may be used even whenthe NPSS and NPBCH are configured as shown in Table 13 or 14. In thissection, for simplicity, the proposed time multiplexing method will bedescribed in more detail based on Table 15, which is a modification ofTable 14.

TABLE 15 Subframe number 0 1 2 3 4 5 6 7 8 9 UL/DL 0 D S U U U D S U U Uconfiguration NPSS NPBCH-A SIB1-NB/NSSS NPBCH-B 1 D S U U D D S U U DNPSS NPBCH-A SIB1-NB/NSSS NPBCH-B 2 D S U D D D S U D D NPSS NPBCH-ASIB1-NB/NSSS NPBCH-B 3 D S U U U D D D D D NPSS NPBCH-A SIB1-NB/NSSSNPBCH-B 4 D S U U D D D D D D NPSS NPBCH-A SIB1-NB/NSSS NPBCH-B 5 D S UD D D D D D D NPSS NPBCH-A SIB1-NB/NSSS NPBCH-B 6 D S U U U D S U U DNPSS NPBCH-A SIB1-NB/NSSS NPBCH-B

In Table 15, the NSSS may be transmitted in subframe 5 of everyodd-numbered (or even-numbered) radio frame, and the SIB1-NB may betransmitted in every even-numbered (or odd-numbered) radio frame withinconsecutive radio frames of 160 msec in order to avoid collision withthe NSSS. Here, transmitting the SIB1-NB in a continuous period of 160msec may mean that the same SIB1-NB may be repeatedly transmitted atregular intervals within 160 msec.

Here, if the repetition number is 16, the SIB1-NB may be transmitted inodd-numbered radio frames when the condition of N_(ID) ^(Ncell) mod 2=1is satisfied. In this case, if the repetition number is 16, the SIB1-NBmay fail to avoid collision with the NSSS. Considering that the TDDsystem is suitable for relatively narrow bandwidth compared to the FDDsystem, a constraint may be configured such that 16 is not used as therepetition number of the SIB1-NB.

As a more specific embodiment, repetition numbers according to the framestructure types as shown in the table below may be proposed. In thiscase, in order to avoid collision with the SIB1-NB, the NSSS may betransmitted in subframe 5 of every odd-numbered radio frame.

TABLE 16 Frame structure Number of NPDSCH Starting radio frame numberfor NB- type repetitions N_(ID) ^(Ncell) SIB1 repetitions (nf mod 256) 1and 2 4 N_(ID) ^(Ncell) mod 4 = 0 0 1 and 2 N_(ID) ^(Ncell) mod 4 = 1 161 and 2 N_(ID) ^(Ncell) mod 4 = 2 32 1 and 2 N_(ID) ^(Ncell) mod 4 = 348 1 and 2 8 N_(ID) ^(Ncell) mod 2 = 0 0 1 and 2 N_(ID) ^(Ncell) mod 2 =1 16 1 16 N_(ID) ^(Ncell) mod 2 = 0 0 1 N_(ID) ^(Ncell) mod 2 = 1 1

FIG. 19 is a diagram schematically illustrating a signaltransmission/reception method between a UE and a BS according to thepresent invention.

As shown in FIG. 19, a UE receives NPSS, NSSS, and the like through afirst carrier (e.g., an anchor carrier) and receives SIB1-NB through asecond carrier (e.g., a non-anchor carrier).

In this case, as shown in FIG. 19, the UE may receive the NPSS throughthe first carrier in an X-th (e.g., X=6) sub-time interval in every timeinterval, and may receive the NSSS through the first carrier in a Y-th(e.g., Y=1) sub-time interval in a corresponding time interval (e.g., anN-th time interval) with a periodicity of two time intervals. Next, whenthe MIB-NB included in the received PBCH indicates that the SIB1-NB istransmitted through the second carrier, the UE may receive the SIB1-NBthrough the second carrier in the Y-th (e.g., Y=1) sub-time interval ina corresponding time interval with a periodicity of one or more timeintervals.

As a specific example, in the case where the SIB1-NB is transmitted witha periodicity of one time interval, the SIB1-NB may be transmittedthrough the second carrier in an 1-th sub-time interval of the N-th timeinterval and an 1-th sub-time interval of the (N+1)-th time interval.

Alternatively, in the case where the SIB1-NB is transmitted with aperiodicity of 2 or 4 time intervals, the SIB1-NB may be transmittedthrough the second carrier during the Y-th sub-time interval in a timeinterval in which the NSSS is not transmitted.

With this configuration, the UE may receive the SIB1-NB withoutcollision with another signal (e.g., NSSS).

As an example applicable to the present invention, when the UE operatesin the LTE TDD system, one time period described above may correspond toone radio frame of the LTE TDD system, and one sub-time interval maycorrespond to one subframe of the LTE TDD system.

As another example, when the UE operates in the LTE TDD system, the LTETDD system may not support UL/DL configuration 0 for one radio framedefined in the LTE system in order to support the NB IoT operation. Inthis case, UL/DL configuration 0 for one radio frame may correspond to“Uplink/Downlink configuration 0” in Table 10.

As an operation corresponding to the operation of the UE describedabove, the BS may transmit the NPSS through the first carrier in theX-th (where X is, for example, 6) sub-time interval of every timeinterval, and transmit the NSSS through the first carrier in the Y-th(e.g., Y=1) sub-time interval in a corresponding time interval (e.g.,the N-th time interval) with a periodicity of 2 time intervals. If theMIB-NB included in the received PBCH indicates that the SIB1-NB istransmitted on the second carrier, the BS may transmit the SIB1-NB onthe second carrier in the Y-th (e.g., Y=1) sub-time interval in acorresponding time interval with a periodicity of one or more timeintervals.

Since examples of the above-described proposal method may also beincluded in one of implementation methods of the present invention, itis obvious that the examples are regarded as a sort of proposed methods.Although the above-proposed methods may be independently implemented,the proposed methods may be implemented in a combined (aggregated) formof a part of the proposed methods. A rule may be defined such that thebase station informs the UE of information as to whether the proposedmethods are applied (or information about rules of the proposed methods)through a predefined signal (e.g., a physical layer signal or ahigher-layer signal).

5. Device Configuration

FIG. 20 is a diagram illustrating construction of a UE and a basestation in which proposed embodiments can be implemented. The UE and thebase station shown in FIG. 20 operate to implement the above-describedembodiments of the signal transmission/reception method between the UEand the base station.

A UE 1 may act as a transmission end on a UL and as a reception end on aDL. A base station (eNB or gNB) 100 may act as a reception end on a ULand as a transmission end on a DL.

That is, each of the UE and the base station may include a Transmitter(Tx) 10 or 110 and a Receiver (Rx) 20 or 120, for controllingtransmission and reception of information, data, and/or messages, and anantenna 30 or 130 for transmitting and receiving information, data,and/or messages.

Each of the UE and the base station may further include a processor 40or 140 for implementing the afore-described embodiments of the presentdisclosure and a memory 50 or 150 for temporarily or permanently storingoperations of the processor 40 or 140.

The UE 1 configured as described above receives NPSS, NSSS, SIB1-NB, andthe like through the receiver 20. In this operation, the UE 1 mayreceive the NPSS and NSSS through a first carrier (e.g., the anchorcarrier) and receive the SIB1-NB through a second carrier (e.g., thenon-anchor carrier). For example, as shown in FIG. 19, if the NSSS isreceived in an 1-th sub-time interval in an N-th time interval, theSIB1-NB may be received in the 1-th sub-time interval in the N+1-th (orN+3-th) time interval.

As a corresponding operation, the base station 100 transmits NPSS, NSSS,SIB1-NB, and the like through the transmitter 110. In this operation,the best station 100 may transmit the NPSS and NSSS through the firstcarrier (e.g., the anchor carrier) and transmit the SIB1-NB through thesecond carrier (e.g., the non-anchor carrier). For example, as shown inFIG. 19, if the NSSS is transmitted in an 1-th sub-time interval in anN-th time interval, the SIB1-NB may be transmitted in the 1-th sub-timeinterval in the N+1-th (or N+3-th) time interval.

The Tx and Rx of the UE and the base station may perform a packetmodulation/demodulation function for data transmission, a high-speedpacket channel coding function, OFDM packet scheduling, TDD packetscheduling, and/or channelization. Each of the UE and the base stationof FIG. 20 may further include a low-power Radio Frequency(RF)/Intermediate Frequency (IF) module.

Meanwhile, the UE may be any of a Personal Digital Assistant (PDA), acellular phone, a Personal Communication Service (PCS) phone, a GlobalSystem for Mobile (GSM) phone, a Wideband Code Division Multiple Access(WCDMA) phone, a Mobile Broadband System (MBS) phone, a hand-held PC, alaptop PC, a smart phone, a Multi Mode-Multi Band (MM-MB) terminal, etc.

The smart phone is a terminal taking the advantages of both a mobilephone and a PDA. It incorporates the functions of a PDA, that is,scheduling and data communications such as fax transmission andreception and Internet connection into a mobile phone. The MB-MMterminal refers to a terminal which has a multi-modem chip built thereinand which can operate in any of a mobile Internet system and othermobile communication systems (e.g. CDMA 2000, WCDMA, etc.).

Embodiments of the present disclosure may be achieved by various means,for example, hardware, firmware, software, or a combination thereof.

In a hardware configuration, the methods according to exemplaryembodiments of the present disclosure may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the methods according to theembodiments of the present disclosure may be implemented in the form ofa module, a procedure, a function, etc. performing the above-describedfunctions or operations. A software code may be stored in the memory 50or 150 and executed by the processor 40 or 140. The memory is located atthe interior or exterior of the processor and may transmit and receivedata to and from the processor via various known means.

Those skilled in the art will appreciate that the present disclosure maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent disclosure. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of thedisclosure should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein. It is obvious to those skilled in the art thatclaims that are not explicitly cited in each other in the appendedclaims may be presented in combination as an embodiment of the presentdisclosure or included as a new claim by a subsequent amendment afterthe application is filed.

The present disclosure is applicable to various wireless access systemsincluding a 3GPP system, and/or a 3GPP2 system. Besides these wirelessaccess systems, the embodiments of the present disclosure are applicableto all technical fields in which the wireless access systems find theirapplications. Moreover, the proposed method can also be applied tommWave communication using an ultra-high frequency band.

What is claimed is:
 1. A method performed by a user equipment operatingin a wireless communication system, the method comprising: receiving anarrowband primary synchronization signal (NPSS), a narrowband secondarysynchronization signal (NSSS), a narrowband physical broadcast channel(NPBCH), and a system information block 1-narrowband (SIB1-NB) via aplurality of radio frames; and performing operations based onsynchronization signals including the NPSS and the NSSS and systeminformation including the SIB1-NB, wherein each of the plurality ofradio frames comprises 10 subframes, wherein the NPSS is received onsubframe #L in each of the plurality of radio frames, wherein the NSSSis received on subframe #N in each of radio frames having even-numberedindex among the plurality of radio frames, wherein the NPBCH is receivedon subframe #K in each of the plurality of radio frames, wherein theNPBCH includes master information block-narrowband (MIB-NB), wherein theSIB1-NB is received on the subframe #N in at least one radio framehaving odd-numbered index among the plurality of radio frames, wherein Nand L are integers, and a difference value between N and L is 5, andwherein K is an integer different from N and L.
 2. The method of claim1, wherein the at least one radio frame is determined based on a numberof narrowband physical downlink shared channel (NPDSCH) repetitions andcell identifier related to the SIB1-NB.
 3. The method of claim 1,wherein the subframe #N where the NSSS is received is adjacent to thesubframe #K where the MIB-NB is received.
 4. The method of claim 1,wherein the 10 subframes included in the each of the plurality of radioframes are indexed from subframe #0 to subframe #9.
 5. The method ofclaim 1, wherein the wireless communication system is a time divisionduplex (TDD) system.
 6. The method of claim 1, wherein the NSSS and theSIB1-NB is received via an identical subcarrier.
 7. A communicationdevice configured to receive signals from a base station in a wirelesscommunication system, the communication device comprising: atransceiver; a memory; and a processor operably coupled with the memoryand storing instructions that, based on being executed by the processor,perform operations comprising: receiving, via the transceiver, anarrowband primary synchronization signal (NPSS), a narrowband secondarysynchronization signal (NSSS), a narrowband physical broadcast channel(NPBCH), and a system information block 1-narrowband (SIB1-NB) via aplurality of radio frames; and performing operations based onsynchronization signals including the NPSS and the NSSS and systeminformation including the SIB1-NB, wherein each of the plurality ofradio frames comprises 10 subframes, wherein the NPSS is received onsubframe #L in each of the plurality of radio frames, wherein the NSSSis received on subframe #N in each of radio frames having even-numberedindex among the plurality of radio frames, wherein the NPBCH is receivedon subframe #K in each of the plurality of radio frames, wherein theNPBCH includes master information block-narrowband (MIB-NB), wherein theSIB1-NB is received on the subframe #N in at least one radio framehaving odd-numbered index among the plurality of radio frames, wherein Nand L are integers, and a difference value between N and L is 5, andwherein K is an integer different from N and L.
 8. The communicationdevice of claim 7, wherein the communication device communicates with atleast one of a mobile terminal, a network and an autonomous vehicle. 9.A communication device configured to transmit signals to a userequipment in a wireless communication system, the communication devicecomprising: a transceiver; a memory; and a processor operably coupledwith the memory and storing instructions that, based on being executedby the processor, perform operations comprising: transmitting, via thetransceiver, a narrowband primary synchronization signal (NPSS), anarrowband secondary synchronization signal (NSSS), a narrowbandphysical broadcast channel (NPBCH), and a system information block1-narrowband (SIB1-NB) via a plurality of radio frames, wherein each ofthe plurality of radio frames comprises 10 subframes, wherein the NPSSis transmitted on subframe #L in each of the plurality of radio frames,wherein the NSSS is transmitted on subframe #N in each of radio frameshaving even-numbered index among the plurality of radio frames, whereinthe NPBCH is transmitted on subframe #K in each of the plurality ofradio frames, wherein the NPBCH includes master informationblock-narrowband (MIB-NB), wherein the SIB1-NB is transmitted on thesubframe #N in at least one radio frame having odd-numbered index amongthe plurality of radio frames, wherein N and L are integers, and adifference value between N and L is 5, and wherein K is an integerdifferent from N and L.
 10. The communication device of claim 9, whereinthe at least one radio frame is determined based on a number ofnarrowband physical downlink shared channel (NPDSCH) repetitions andcell identifier related to the SIB1-NB.
 11. The communication device ofclaim 9, wherein the subframe #N where the NSSS is transmitted isadjacent to the subframe #K where the MIB-NB is transmitted.
 12. Thecommunication device of claim 9, wherein the 10 subframes included inthe each of the plurality of radio frames are indexed from subframe #0to subframe #9.
 13. The communication device of claim 9, wherein thewireless communication system is a time division duplex (TDD) system.14. The communication device of claim 9, wherein the NSSS and theSIB1-NB is transmitted via an identical subcarrier.